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ftString

ftString = 1

Example​

function IsNarrowString(Field: TField): Boolean;
begin
  Result := Field.DataType = ftString;
end;

Usage​

ftString identifies variable narrow character data whose Size and ANSI conversion behaviour come from the field and provider.

Additional Technical Info​

ftString is declaration ordinal 1 of TFieldType. It identifies a normal variable-length field in Delphi's traditional narrow/ANSI string family.

The installed RTL maps it to TStringField. A new field defaults to Size = 20, but provider or persistent field metadata determines the live capacity; never infer a database column's length from that constructor default. The class supports conversions to Boolean, numeric, date/time and GUID values, but those conversions use Delphi parsing rules and can raise errors. The enum itself promises only the field family.

On the current Windows build, ANSI conversion can depend on the process/system code page. Assigning Unicode characters that are not representable can be lossy. Use ftWideString for Unicode data where supported. Treat Size as provider metadata, not a universal UTF-8 byte limit: characters, UTF-16 code units and encoded bytes can have different counts.

Null is distinct from ''. Provider collation, trailing-space treatment and case sensitivity control database comparisons; a Delphi string comparison may not reproduce them. Validate and truncate deliberately before assignment because drivers can reject, truncate or transform oversized values differently.

The example only inspects metadata and was source-reviewed; no encoding, parsing, dataset, database, runtime or image test ran.

External references

Created 2026-07-15